1. Field of the Invention
This invention relates to read-while-write magnetic recording apparatus. More specifically, the invention relates to a magnetic head assembly for read-while-write recording apparatus.
2. Descriotion Relative to the Prior Art
In a magnetic recording apparatus, either tape or disk, a read-while-write capability is an essential feature for providing error free magnetically stored data. A read-while-write head assembly comprises a record head in-line with a playback head, with the read head closely positioned downstream of the record head in the direction of media motion. By continually reading "just recorded" data while writing, the integrity or quality of the recorded data is immediately determined at a time while the original data is still available in temporary storage in the recording system. If data contained within a certain data block cannot be successfully read, the entire data block is re-recorded at a different location on the media, and a flag is set to inform the playback electronics that the previous recorded version of the data block is incorrect and should be ignored.
When reading-while-writing data, a signal radiated from the record head and electronics to the playback head and electronics, referred to hereinafter as crosstalk, can cause excessive amounts of noise. Crosstalk during a read-while-write operation of magnetic recording apparatus can be, for example, the result of propagation of electric and magnetic fields from sources such as the coil of the record head and leads between the coil and recording electronics.
It is understood by those skilled in the art that read-while-write capability in magnetic recording apparatus imposes stringent geometry and spatial considerations for reading "just recorded" data. Direct crosstalk between the "paired" heads can be overcome by providing for a greater separation therebetween. However, a larger spacing introduces a larger delay between the time data is recorded and when that data is played back, thereby requiring a larger temporary storage for original data. Furthermore, a larger spacing increases the possibility that there will be misalignment between the two heads, thereby introducing a tracking error. This problem can be very severe for a high-density recorder having narrow recording tracks.
A solution to the misalignment problem is an integrated read-write head. The disclosure of U.S. Pat. No. 3,908,194 is exemplary of an integrated read-while-write head assembly having an inductive record - MR playback head combined on the same surface of a substrate. In an attempt to overcome the problem of direct crosstalk between the record and playback heads, the integrated head employs various shielding layers to isolate the MR element of the playback head from fields of the inductive record head. This solution, however, contributes significantly to the complexity of the combined head, thereby adding to manufacturing cost, increasing assembly time, and reducing manufacturing yield. Furthermore, in order to fit into the limited space of a read-while-write head assembly, gaps must often be left in a shield for such things as wires or ventilation. Gaps or discontinuities present in a shield reduce shielding effectiveness.